Optical disk reproduction apparatus and method for controlling optical disk reproduction apparatus

ABSTRACT

An optical disk reproduction apparatus comprising a microcomputer ( 7 ) for resuming reading data from an optical disk ( 1 ) when buffering to a memory ( 6 ) is interrupted, a continuous data detector ( 55 ) for dividing first data buffered in the memory ( 6 ) before the buffering interruption and second data read out in accordance with an instruction from the microcomputer ( 7 ) into “n” groups, respectively, and detecting whether the first data and the second data are in coincidence for each group, and a buffering resumption request generating circuit ( 56 ) for instructing a timing of buffering resumption on the basis of a result of the continuous data detector ( 55 ).

TECHNICAL FIELD

The present invention relates to an optical disk reproduction apparatusand a method for controlling an optical disk reproduction apparatus and,more particularly, to an optical disk reproduction apparatus which cansuccessively reproduce data recorded on an optical disk and a method forcontrolling the optical disk reproduction apparatus.

BACKGROUND ART

An optical disk reproduction apparatus has a servo for controllingrotation of an optical disk and a position of an optical pickup so as tocorrectly read out data recorded on the disk at a constant rate. Theservo is easily affected by vibrations, or flaws or dusts on the diskand thus, reading of data is sometimes interrupted. Therefore, ashockproof function is required to resume reading of data from anappropriate position so as to prevent data from being outputdiscontinuously, even when the reading of data is interrupted. At thistime, since a position where the reading of data is to be resumed cannotbe decided only by the control of a position of the optical pickup, theabove-described position for resumption is Usually decided after thedata is confirmed by using the shockproof function.

FIG. 5 is a block diagram illustrating a structure of a prior artmusical CD reproduction apparatus. A disk 21 is a CD having musical datarecorded thereon. An optical pickup 22 irradiates a laser light to thedisk 21 to read the musical data recorded on the disk 21. An analogsignal processing unit 23 obtains conditions of tracking and focusingfrom the data read by the optical pickup 22 as well as binarizes thedata read by the optical pickup 22. A servo 24 controls the tracking andthe focusing of the optical pickup 22. A digital signal processing unit25 comprises a CIRC (Cross-Interleave-Reed-Solomon Code) processing unit251, a formatting circuit 252, a memory arbitration circuit 253, anoutput data FIFO memory 254, a comparator 255, and a bufferingresumption request generating circuit 256, and processes data binarizedby the analog signal processing unit 23 to output processed data asreproduced data. A memory 26 temporarily stores the data processed bythe digital signal processing unit 25. A microcomputer 27 obtainsinformation from the respective elements and controls operations of therespective elements.

An operation of the prior art musical CD reproduction apparatus will bedescribed. The optical pickup 22 irradiates a laser light to the disk 21and converts a light reflected from the disk 21 into a signal to outputthe signal to the analog signal processing unit 23. The analog signalprocessing unit 23 outputs conditions of tracking and focusing to theservo 24 on the basis of the signal from the optical pickup 22 as wellas binarizes the signal from the optical pickup 22 to output a binarizedsignal to the digital signal processing unit 25. The servo 24 outputs acontrol signal to the optical pickup 22 on the basis of the informationfrom the analog signal processing unit 23 to control the tracking andthe focusing. The CIRC processing unit 251 performs, for the binarizeddata, EFM (Eight to Fourteen Modulation) demodulation, separation of CD(Compact Disk)-DA (Digital Audio) data from subcode data, and errorcorrection processing for the CD-DA data, and outputs processed data tothe formatting circuit 252. The formatting circuit 252 converts theCD-DA data output from the CIRC processing unit 251 into a prescribedformat and then outputs converted data to the memory 26 via the memoryarbitration circuit 253. Data buffered in the memory 26 is read out at aprescribed rate to be sent to the output data FIFO memory 254 via thememory arbitration circuit 253, and output the same as reproduced data.An amount of the data stored in the memory 26, being controlled by the.microcomputer 27, does not exceed a capacity of the memory 26.

During reproduction from the disk 21, when the microcomputer 27 detects,on the basis of the information from the servo 24, that an error occursin the reading of data, the microcomputer 7 instructs the digital signalprocessing unit 25 to interrupt the buffering as well as instructs theservo 24 to move the optical pickup 22 to a position before the positionof data where the reading error occurs on the disk 21. In addition, thelatest block of data buffered in the memory 26 is kept in the comparator255 as expectation data.

The comparator 255 captures the CD-DA data read out from the disk 21after the optical pickup 22 moves, and compares the CD-DA data with theexpectation data. The comparator 255 outputs “H” when all the data arein coincidence, and outputs “L” when at least one of the data is inuncoincidence, to the buffering resumption request generating circuit256.

When the buffering resumption request generating circuit 256 receives“H” from the comparator 255, the buffering resumption request generatingcircuit 256 requests the formatting circuit 252 to resume the buffering,and then the formatting circuit 252 resumes the buffering from datafollowing to the CD-DA data which is judged in coincidence by thecomparator 255. On the other hand, when the buffering resumption requestgenerating circuit 256 receives “L” from the comparator 255, themicrocomputer 27 instructs the servo 24 to move the optical pickup 22 toa further forward position, and continues to compare the CD-DA data withthe expectation data until the comparator 255 outputs “H”.

Usually, when the CD-DA data is reproduced by an optical diskreproduction apparatus having the above-described structure, the dataread out from the disk 21 is controlled to be read out at a higher ratethan that of data output as reproduced data from the output data FIFOmemory 254. That is, a rate of buffering data in the memory 26 is higherthan a rate of reading out data from the memory 26. Therefore, even whenthe buffering to the memory 26 is interrupted, the output data FIFOmemory 254 reads out the data stored in the memory 26 at a prescribedrate and outputs reproduced data. That is, while data is stored in thememory 26, the optical disk reproduction apparatus can output reproduceddata continuously.

In addition, Japanese Published Patent Application No.Hei.9-17124discloses another shockproof function utilizing subcode data. When thebuffering is interrupted, the shockproof function disclosed herein readsout and holds time information contained in subcode data which iswritten last, returns a CD pickup unit to an interruption point, thencompares time information of subcode data included in data read outthereat with the time information held at the interruption, andinstructs a timing of the buffering resumption.

On the other hand, when data is read out by the optical diskreproduction apparatus, errors may creep in the data. Further, there isa possibility that errors still remain in data after error correction isperformed and that the data containing the errors are output asreproduced data. Here, in many cases, the errors contained in thereproduced data are of a negligible level. Particularly, in case of amusical CD where adjacent data have high correlations, even if a fewerrors are contained in the reproduced data, the errors cannot berecognized by the human ear in many cases.

In the prior art optical disk reproduction apparatus as described above,errors occurring also during a usual reproduction, independent of thebuffering interruption, may be contained in the expectation data held inthe comparator 255 and the CD-DA data. Therefore, in some cases, thecomparator 255 cannot confirm coincidence of all data sequences andthus, the buffering cannot be resumed.

The present invention is made to solve the above problems, and it is anobject of the present invention to provide an optical disk reproductionapparatus which can appropriately instruct buffering resumption, evenwhen errors occurring in data independent of the buffering interruptionare contained.

In addition, in the method disclosed in Japanese Published PatentApplication No.Hei.9-17124, since the CD-DA data is not buffered bydirectly utilizing the time information of subcode data, a timing of thebuffering and a timing of reading subcode data do not always completelycoincide. Therefore, when the buffering is resumed on the basis of theconfirmation of only the subcode data, it may occur that discontinuousdata are buffered.

The present invention is made to solve the above problems, and it is anobject of the present invention to provide an optical disk reproductionapparatus and a controlling method therefor, which apparatus canappropriately instructs the buffering resumption without utilizing thesubcode data.

DISCLOSURE OF THE INVENTION

The present invention provides an optical disk reproduction apparatuswhich receives a reflected light obtained by irradiating a laser lightto an optical disk thereby reading data recorded on the optical disk,temporarily buffers the data in a successively rewritable memory havinga prescribed capacity, and then outputs the data as reproduced data, andcomprises control means for resuming reading the data from the opticaldisk when buffering to the memory is interrupted, data coincidencedetecting means for dividing first data buffered in the memory beforethe buffering interruption and second data read out by the control meansinto “n” groups, respectively, and detecting whether the first data andthe second data are in coincidence for each group, and a bufferingresumption request generating circuit for instructing a timing ofbuffering resumption on the basis of a result of the data coincidencedetecting means.

Further, in the present invention, the data coincidence detecting meansfurther comprises plural comparators each of which holds the first dataand the second data, which are divided into the plural groups, one groupby one, and compares the both data to decide whether each group of thedivided data are in coincidence, an adder for obtaining a total numberof the groups, for which groups it is decided that the first data andthe second data are in coincidence, and a subtracter for obtaining avalue of (a prescribed decision threshold)−(the total number)/(the valueof “n”), and the buffering resumption request generating circuitinstructs the timing of buffering resumption when the value obtained bythe subtracter is 0 or less.

Further, in the present invention, the decision threshold can be setmanually.

Further, in the present invention, the decision threshold is a ratio ofan amount of data which is correctly reproduced to an amount of datawhich is reproduced by the optical disk reproduction apparatus.

Further, the present invention provides a control method for controllingan optical disk reproduction apparatus which receives a reflected lightobtained by irradiating a laser light to an optical disk thereby readingdata recorded on the optical disk, temporarily buffers the data in asuccessively rewritable memory having a prescribed capacity, and thenoutputs the data as reproduced data, and comprises a control step forresuming reading the data from the optical disk when buffering to thememory is interrupted, a data coincidence detecting step for dividingfirst data buffered in the memory before the buffering interruption andsecond data read out in the control step into “n” groups, respectively,and detecting whether the first data and the second data are incoincidence for each group, and a buffering resumption request step forinstructing a timing of buffering resumption, on the basis of a resultof the data coincidence detecting step.

Further, the present invention provides a storage medium storing aprogram code for executing the optical disk reproduction apparatuscontrol method.

Further, in the present invention, the data coincidence detecting stepfurther comprises a comparison step for holding the first data and thesecond data, which are divided into the plural groups, one group by one,and comparing the both data thereby deciding whether the data are incoincidence, an addition step for obtaining a total number of thegroups, for which groups it is decided that the first data and thesecond data are in coincidence, and a subtraction step for obtaining avalue of (a prescribed decision threshold)−(the total number)/(the valueof “n”), and the buffering resumption request step instructs the timingof buffering resumption when the value obtained in the subtraction stepis 0 or less.

Further, the present invention provides a storage medium storing aprogram code for executing the optical disk reproduction apparatuscontrol method.

According to the present invention, when the buffering to a memory isinterrupted for some reason, the optical disk reproduction apparatus canresume the reading of data from the optical disk, divide each of thefirst data buffered in the memory before the buffering interruption andthe second data read out after the buffering interruption into pluralgroups, and detect whether the first data and the second data are incoincidence for each group, and instruct the timing of bufferingresumption on the basis of that result. Therefore, even if an erroroccurring also at normal reproduction, independent of the bufferinginterruption, is contained in data to be compared, the bufferingresumption can be instructed appropriately.

In addition, according to the present invention, the optical diskreproduction apparatus instructs the timing of buffering resumption byutilizing the CD-DA data. Therefore, the timing of buffering can beinstructed more correctly, with relative to an optical disk reproductionapparatus and a control method therefor, in which the timing of thebuffering resumption is instructed by utilizing only the subcode data.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a structure of an optical diskreproduction apparatus according to a preferred embodiment of thepresent invention.

FIG. 2 is a flowchart for explaining an operation of the optical diskreproduction apparatus when a reading error occurs during thereproduction from an optical disk.

FIG. 3 is a block diagram illustrating structures of a continuous datadetector and a buffering resumption request generating circuit.

FIG. 4 is a flowchart for explaining operations of the continuous datadetector and the buffering resumption request generating circuit.

FIG. 5 is a block diagram illustrating a structure of a prior artmusical CD reproduction apparatus.

BEST EMBODIMENTS FOR EXECUTING THE INVENTION

Hereinafter, the present invention will be described in more detail,with reference to the accompanying drawings.

FIG. 1 is a block diagram illustrating a structure of an optical diskreproduction apparatus according to a preferred embodiment of thepresent invention. An optical disk 1 is a CD having musical datarecorded thereon. An optical pickup 2 irradiates a laser light to theoptical disk 1 to read the musical data recorded on the optical disk 1.An analog signal processing unit 3 obtains conditions of tracking andfocusing from the data read by the optical pickup 2 as well as binarizesthe data read by the optical pickup 2. A servo 4 controls the trackingand the focusing of the optical pickup 2. A digital signal processingunit 5 comprises a CIRC processing unit 51, a formatting circuit 52, amemory arbitration circuit 53, an output data FIFO memory 54, acontinuous data detector 55, and a buffering resumption requestgenerating circuit 56, and processes data binarized by the analog signalprocessing unit 3 to output processed data as reproduced data. A memory6 temporarily stores the data processed by the digital signal processingunit 5. A microcomputer 7 obtains information from the respectiveelements and controls operations of the respective elements.

An operation of the optical disk reproduction apparatus according to thepreferred embodiment will be described. The optical pickup 2, beingcontrolled by the servo 4, irradiates a laser light to the optical disk1 and converts a light reflected from the optical disk 1 into a signal,and outputs the signal to the analog signal processing unit 3. Theanalog signal processing unit 3 outputs conditions of tracking andfocusing to the servo 4 on the basis of the signal from the opticalpickup 2 as well as binarizes the signal from the optical pickup 2 tooutput a binarized signal to the digital signal processing unit 5. Theservo 4 outputs a control signal to the optical pickup 2 on the basis ofthe information from the analog signal processing unit 3, therebycontrolling the tracking and the focusing.

The digital signal processing unit 5 receives the data binarized by theanalog signal processing unit 3 in the CIRC processing unit 51, and theCIRC processing unit 51 performs the EFM demodulation, the separation ofCD-DA data from subcode data, and the error correction processing of theCD-DA data, and outputs processed data to the formatting circuit 52. Theformatting circuit 52 converts the CD-DA data output from the CIRCprocessing unit 51 into a prescribed format, and buffers converted datain the memory 6 via the memory arbitration circuit 53. The data bufferedin the memory 6 is read out to be sent to the output data FIFO memory 54via the memory arbitration circuit 53 at a prescribed rate, and outputthe same as reproduced data. The data output from the output data FIFOmemory 54 is controlled to be read out at a lower rate than that of thedata read out from the optical disk 1. That is, a rate of buffering datain the memory 6 is higher than a rate of reading out data from thememory 6. The buffering into the memory 6 is controlled by themicrocomputer 7, according to a capacity of the memory 6.

When the buffering of the CD-DA data into the memory 6 is interruptedfor some reason and thereafter the reading from the disk 1 is resumed,the continuous data detector 55 detects whether data before thebuffering interruption and data after the reading resumption coincide.According to the result of the continuous data detector 55, thebuffering resumption request generating circuit 56 instructs a timing ofbuffering resumption to the formatting circuit 52.

FIG. 2 is a flowchart for explaining an operation of the optical diskreproduction apparatus, when the microcomputer 7 detects that an erroroccurs in the reading of data during the reproduction from the opticaldisk 1, on the basis of the information from the servo 4 and the digitalsignal processing unit 5. The operation of the optical disk reproductionapparatus in case a reading error occurs will be described withreference to FIGS. 1 and 2.

When an error occurs in the data reading, the digital signal processingunit 5 interrupts the buffering in accordance with an instruction fromthe microcomputer 7 in step S1. Next, in step S2, the servo 4 moves theoptical pickup 2 to a position before a position of data where a readingerror occurs on the optical disk 1, in accordance with an instructionfrom the microcomputer 7. The position to which the optical pickup 2 isto be moved is decided on the basis of an address of the data which hasalready been read out.

Then, in step S3, the continuous data detector 55 divides a datasequence of a block, which is one block before the block for which thebuffering is interrupted among the data stored in the memory 6, into npieces (n is an integer which is 2 or more) of data, and holds divideddata sequences as expectation data sequences, in accordance with aninstruction from the microcomputer 7.

In step S4, after moving its position in accordance with an instructionfrom the servo 4, the optical pickup 2 reads out a data sequence of oneblock from the optical disk 1. Instep S5, the analog signal processingunit 3 binarizes the read out data sequence. In step S6, the CIRCprocessing unit 51 performs the above-described processings to abinarized data sequence to generate a CD-DA data sequence, and outputthe CD-DA data sequence to the continuous data detector 55.

In step S7, the continuous data detector 55 divides the CD-DA datasequence into n pieces as in step S3 to capture the divided datasequences, and decides whether the expectation data sequence and theCD-DA data sequence are the same for each divided data sequence. When itis decided that the both data are the same (YES) in step S7, theprocessing goes to step S8 and the buffering resumption requestgenerating circuit 56 outputs a buffering resumption trigger signal tothe formatting circuit 52. The trigger signal is output in such a timingthat the CD-DA data which is output from the CIRC processing unit 51 canbe buffered immediately after it is decided YES in step S7. Whendetecting the buffering resumption trigger signal, the formattingcircuit 52 converts the CD-DA data into a prescribed format and resumesthe buffering to the memory 6 (step S9).

On the other hand, when it is decided that the both data are not thesame (NO) in step S7, the processing goes to step S20 and themicrocomputer 7 instructs the servo 4 to move the optical pickup 2 to afurther forward position. Thereafter, the processing goes back to stepS4 and the above operations are repeated. Here, the operations fromsteps S1 to S3 can be performed in random order.

Structures and operations of the continuous data detector 55 and thebuffering resumption request generating circuit 56 will be described inmore detail. FIG. 3 is a block diagram illustrating the structures ofthe continuous data detector 55 and the buffering resumption requestgenerating circuit 56. The continuous data detector 55 comprisescomparators 11-1 to 11-n for dividing each of the expectation datasequence and the CD-DA data sequence into “n” groups, respectively, andcomparing data sequences for each group, an adder 12 for obtaining atotal number of groups, for which groups it is decided that theexpectation data sequence and the CD-DA data sequence are the same, anda subtracter 13 for comparing a calculation result of the adder 12 witha continuous data decision threshold R.

FIG. 4 is a flowchart for explaining operations of the continuous datadetector 55 and the buffering resumption request generating circuit 56,and shows steps S3, S7, and S8 in the flowchart of FIG. 2 in moredetail. The operations of the continuous data detector 55 and thebuffering resumption request generating circuit 56 will be describedwith reference to FIGS. 1 to 4.

In step S100 (corresponding to step S3 in FIG. 2), the comparators 11-1to 11-n divide a data sequence of a block just before the block, forwhich block the buffering is interrupted among blocks of the data storedin the memory 6, into “n” groups, and captures the divided datasequence, one group by one, as an expectation data sequence. Forexample, when a data sequence comprises 200 pieces of data, the datasequence is divided into 10 (=n) groups successively from the head, eachgroup comprising 20 pieces of data. Then, the data sequences dividedinto 10 groups are input to the 10 comparators, one group by one.

When the CD-DA data is generated in step S6 of FIG.2, the comparators11-1 to 11-n divide a CD-DA data sequence into n pieces and capture thedivided CD-DA data sequences, respectively, in step S101, as in stepS100.

In step S102, each of the comparators 11-1 to 11-n compares the CD-DAdata sequence with the expectation data sequence, and decides whethereach pair of the expectation data sequences and the CD-DA datasequences, which are divided into n pieces, respectively, are incoincidence. To the adder 12, “H” is output when the both data sequencesare in coincidence, and “L” is output when the both data sequences arein uncoincidence.

In step S110, the adder 12 additionally counts the number of “H”, whichare output from the comparators 11-1 to 11-n to obtain the total numberm. In step S111, the adder 12 obtains a value m/n and output the valuem/n to the subtracter 13.

In step S120, the subtracter 13 subtracts the value m/n from thecontinuous data decision threshold R set by the microcomputer 7, andoutputs a value R−m/n to the buffering resumption request generatingcircuit 56. Here, the continuous data decision threshold R can be freelyset by the microcomputer 7. For example, a normal data reproductionratio which means a ratio of correct reproduction by the optical diskreproduction apparatus can be set as R (for example, when 90% of data iscorrectly reproduced, R={fraction (9/10)}). Or, an arbitrary value canbe input by a user. When R=1, it means that the data recorded on anoptical disk and the reproduced data are completely the same. When R isset in consideration of the rate of data reproduction at normal states,it can be judged whether an error included in data to be compared comesfrom the buffering interruption or comes from the errors generated bythe normal reproduction.

In step S130, the buffering resumption request generating circuit 56decides whether the value of R−m/n is 0 or less, i.e., whether thecompared CD-DA data is in coincidence with the expectation data. When itis decided in step S130 that the value of R−m/n is 0 or less (YES),i.e., the compared CD-DA data is in coincidence with the expectationdata, the processing goes to step S131 (corresponding to step S8 in FIG.2) and the buffering resumption request generating circuit 56 generatesa buffering resumption trigger signal and outputs the trigger signal tothe formatting circuit 52. The formatting circuit 52 which has receivedthe trigger signal resumes the buffering (step S9).

When it is decided in step S130 that R−m/n is not 0 or less (NO), i.e.,the compared CD-DA data is in uncoincidence with the expectation data,the processing goes to step S133 and the buffering resumption requestgenerating circuit 56 requests the microcomputer 7 to move the opticalpickup 2, and then the processing goes back to step S101.

In the optical disk reproduction apparatus according to the preferredembodiment of the present invention, the rate of buffering data into thememory 6 is controlled to be higher than the rate of reading out datafrom the memory 6. Therefore, even if the buffering into the memory 6 isinterrupted, the output data FIFO memory 54 reads out data stored in thememory 6 at a prescribed rate and continues to output reproduced data,while the data are being stored in the memory 6. The above-describedsteps S2 to S9 are carried out while the output data FIFO memory 54 areoutputting the reproduced data.

As described above, the optical disk reproduction apparatus of thepreferred embodiment divides the expectation data and the CD-DA datainto plural groups to perform comparison, and decides the timing forbuffering resumption on the basis of the number of groups which are incoincidence and the continuous data decision threshold R. Therefore,when R is decided in consideration of the data reproduction ratio atnormal states, it can be judged whether an error included in data to becompared comes from the buffering interruption or comes from the errorgenerated by normal reproduction, which enables instructing thebuffering resumption appropriately.

In addition, the optical disk reproduction apparatus according to thepreferred embodiment can instruct the timing of buffering resumptionmore correctly, because it utilizes not the subcode data but the CD-DAdata.

In the foregoing, the optical disk reproduction apparatus which canappropriately instruct the buffering resumption when errors occur inreading from the optical disk for some reason, is described. However,the above-described embodiment can also be applied to the control ofdata which is to be buffered into the memory 6. That is, since the rateof outputting the reproduced data is smaller than the rate of bufferingdata into the memory 6, when it comes to a state where data are storedin the memory 6 to its uppermost capacity, the buffering to the memory 6is interrupted. Even in case where such buffering interruption occurs,if the microcomputer 7 is set such that the operation described in theflowchart of FIG. 2 is carried out, the buffering resumption can beinstructed correctly without deteriorating the continuity in thereproduced data.

In addition, the present invention can be applied not only to anapparatus for reproducing an optical disk having CD-DA data recordedthereon but also to an apparatus for reproducing an optical disk whichis used as a Read Only Memory (ROM) for a computer. In the latter case,it is required to add a function of a CD-ROM decoder to the optical diskreproduction apparatus of the above-described embodiment.

Further, the object of the present invention is achieved by amicrocomputer in an optical disk reproduction apparatus performingreading from a storage medium having a program code of a software whichrealizes the function of the embodiment recorded thereon. Therefore, thestorage medium having the program code recorded thereon constitutes thepresent invention.

APPLICABILITY IN INDUSTRY

As described above, the optical disk reproduction apparatus and thecontrol method therefor according to the present invention areappropriately applied to an apparatus for reproducing an optical diskwhich has CD-DA data recorded thereon or which is used as a Read OnlyMemory (ROM) for a computer.

What is claimed is:
 1. A reproduction apparatus for receiving areflected light obtained by irradiating laser light on an optical diskfor reading data recorded on such optical disk, temporarily bufferingthe read data in a successively rewritable memory having a prescribedcapacity, and then outputting the read data as reproduced data,comprising: control means for resuming reading data from an optical diskwhen buffering read data to the memory is interrupted; data coincidencedetecting means for dividing first data buffered in the memory beforethe buffering interruption and second data read out by the control meansinto “n” groups, respectively, and detecting whether the first data andthe second data are in coincidence for each group; and a bufferingresumption request generating circuit for instructing a timing ofbuffering resumption on the basis of a result of the data coincidencedetecting means.
 2. The reproduction apparatus of claim 1, wherein thedata coincidence detecting means further comprises: plural comparatorseach for holding the first data and the second data, and comparing theheld first and second data to decide whether each group of the divideddata are in coincidence, and identifying coincident groups of data; anadder for obtaining a total number of the coincident groups; and asubtracter for obtaining a value of: (a prescribed decisionthreshold)−(the total number)/(the value of “n”), and the bufferingresumption request generating circuit for instructing a timing ofbuffering resumption when the value obtained by the subtracter is atmost zero.
 3. The reproduction apparatus of claim 2, wherein thedecision threshold comprises a manually set decision threshold.
 4. Thereproduction apparatus of claim 2, wherein the decision threshold isdefined as a ratio of a first amount of data that is correctlyreproduced to a second amount of data that is reproduced by the opticaldisk reproduction apparatus.
 5. A method for controlling a reproductionapparatus for receiving reflected light obtained by irradiating laserlight on an optical disk for reading data recorded on such optical disk,temporarily buffering the read data in a successively rewritable memoryhaving a prescribed capacity, and then outputting the read data asreproduced data, the method comprising: resuming reading data from anoptical disk when reading data and buffering the read data to the memoryis interrupted; dividing first data buffered in the memory before thebuffering interruption and second data read out in said resuming readinginto “n” groups, respectively, and detecting whether the first data andthe second data are in coincidence for each group; and resumingbuffering on the basis of a result of said dividing first data.
 6. Themethod of claim 5, wherein said dividing first data further comprises:holding the first data and the second data, comparing the held first andsecond data to determine whether the data are in coincidence, andidentifying coincident groups; obtaining a total number of thecoincident groups; and obtaining a value of:  (a prescribed decisionthreshold)−(the total number)/(the value of “n”), and said resumingbuffering further comprises timing buffering resumption when saidobtained value is at most zero.
 7. A computer-readable storage mediumstoring a program code for executing a method for controlling areproduction apparatus for receiving reflected light obtained byirradiating laser light on an optical disk for reading data recorded onthe optical disk, temporarily buffering the read data in a successivelyrewritable memory having a prescribed capacity, and then outputting thedata as reproduced data, the method comprising: resuming reading datafrom an optical disk when reading data and buffering the read data tothe memory is interrupted; dividing first data buffered in the memorybefore the buffering interruption and second data read out in saidreading into “n” groups, respectively, and detecting whether the firstdata and the second data are in coincidence for each group; and resumingbuffering on the basis of a result of said dividing first data.
 8. Acomputer-readable storage medium storing a program code for executing amethod for controlling a reproduction apparatus for receiving reflectedlight obtained by irradiating laser light on an optical disk for readingdata recorded on the optical disk, temporarily buffering the read datain a successively rewritable memory having a prescribed capacity, andthen outputting the data as reproduced data, the method comprising:resuming reading data from an optical disk when reading data andbuffering the read data to the memory is interrupted; dividing firstdata buffered in the memory before the buffering interruption and seconddata read out in said resuming reading into “n” groups, respectively,and detecting whether the first data and the second data are incoincidence for each group, wherein the dividing first data furthercomprises: holding the first data and the second data, comparing theheld first and second data to determine whether the data are incoincidence, and identifying coincident groups; obtaining a total numberof the coincident groups; and obtaining a value of: (a prescribeddecision threshold)−(the total number)/(the value of “n”); and resumingbuffering when the obtained value is at most zero.